Implantable lead for septal placement of electrode with fixation mechanism in the pulmonary artery

ABSTRACT

A lead body includes an electrode coupled to an intermediate portion of the lead body. A distal end of the lead includes a pre-formed, biased shape adapted to passively fixate the distal end of the lead within a pulmonary artery with the electrode positioned in the right ventricle or ventricular outflow tract. The lead body can include a pre-formed J-shape, with the electrode coupled to the intermediate portion of the lead body and located distally from a bottom of the pre-formed J-shape. The lead body can include a section of the intermediate portion of the lead body being less stiff than adjacent sections of the lead body with the electrode coupled to the intermediate portion of the lead body and located distally from the less stiff section.

CROSS REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No. 10/325,658, filed on Dec. 19, 2002, the specification of which is incorporated herein by reference.

FIELD OF THE INVENTION

This invention relates to the field of medical leads, and more specifically to an implantable lead.

BACKGROUND

Leads implanted in or about the heart have been used to reverse certain life threatening arrhythmia, or to stimulate contraction of the heart. Electrical energy is applied to the heart via an electrode to return the heart to normal rhythm. Leads are usually positioned in the ventricle or in the atrium through a subclavian vein, and the lead terminal pins are attached to a pacemaker which is implanted subcutaneously.

For example, one approach is to place the electrode against the ventricular septum above the apex. However, current leads require a lead placed with the electrode against the septum above the apex to be actively fixated. This may possibly result in trauma to the heart from cyclical heart motion, and lead to micro-dislodgement of the electrode, and relatively higher defibrillating and pacing thresholds. Moreover, other factors which can be improved include better electrode contact, and easier implanting and explanting of the leads.

SUMMARY

A lead body having an electrode coupled to an intermediate portion of the lead body. A distal end of the lead includes a pre-formed, biased shape adapted to passively fixate the distal end of the lead within a pulmonary artery with the electrode positioned at the ventricular septum or ventricular outflow tract.

Another aspect includes a lead body configured into a pre-formed J-shape. The lead includes an electrode coupled to an intermediate portion of the lead body and located distally from a bottom of the pre-formed J-shape. The lead is adapted to be placed within a heart in a J-shaped configuration with the bottom of the J-shape within the right ventricle and the electrode positioned at a ventricular septum or a right ventricular outflow tract such that at least a portion of the distal end of the lead body is located within a pulmonary artery.

Another aspect includes a lead body having a section of the intermediate portion of the lead body being less stiff than adjacent sections of the lead body. The lead includes an electrode coupled to the intermediate portion of the lead body and located distally from the less stiff section. The lead is adapted to be placed within a heart in a J-shaped configuration with the less stiff section near a bottom of the J-shape such that the electrode is positioned at a ventricular septum or a right ventricular outflow tract and at least a portion of the distal end of the lead body is located within a pulmonary artery. In one example, the distal end is actively fixated within the pulmonary artery.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a view of a lead, according to one embodiment, implanted within a heart.

FIG. 2 shows a distal portion of a lead according to one embodiment.

FIG. 3 shows a distal portion of a lead according to one embodiment.

FIG. 4 shows a distal portion of a lead according to one embodiment.

FIG. 5 shows a view of a lead, according to one embodiment, implanted within a heart.

FIG. 6 shows a front view of a lead according to one embodiment.

FIG. 7 shows an intermediate portion of a lead according to one embodiment.

FIG. 8 shows a view of a lead, according to one embodiment, implanted within a heart.

DETAILED DESCRIPTION

In the following detailed description, reference is made to the accompanying drawings which form a part hereof, and in which is shown by way of illustration specific embodiments in which the invention may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention, and it is to be understood that other embodiments may be utilized and that structural changes may be made without departing from the scope of the present invention. Therefore, the following detailed description is not to be taken in a limiting sense, and the scope of the present invention is defined by the appended claims and their equivalents.

FIG. 1 shows a view of a lead 100 implanted within a heart 10. Heart 10 generally includes a superior vena cava 12, a right atrium 14, a right ventricle 16, a right ventricular apex 17, a ventricular septum 18, and a ventricular outflow tract 20, which leads to a pulmonary artery 22. In one embodiment, lead 100 is adapted to deliver defibrillation shocks to heart 10. Lead 100 is part of an implantable system including a pulse generator 110, such as a defibrillator.

Pulse generator 110 can be implanted in a surgically-formed pocket in a patient's chest or other desired location. Pulse generator 110 generally includes electronic components to perform signal analysis, processing, and control. Pulse generator 110 can include a power supply such as a battery, a capacitor, and other components housed in a case. The device can include microprocessors to provide processing and evaluation to determine and deliver electrical shocks and pulses of different energy levels and timing for ventricular defibrillation, cardioversion, and pacing to heart 10 in response to cardiac arrhythmia including fibrillation, tachycardia, and bradycardia.

In one embodiment, lead 100 includes a lead body 105 extending from a proximal end 107 to a distal end 109 and having an intermediate portion 111. Lead 100 includes one or more conductors, such as coiled conductors or other conductors, to conduct energy from pulse generator 110 to heart 10, and also to receive signals from the heart. The lead further includes outer insulation 112 to insulate the conductor. The conductors are coupled to one or more electrodes, such as electrodes 120, 122, 124, and 126. Lead terminal pins are attached to pulse generator 110. The system can include a unipolar system with the case acting as an electrode or a bipolar system with a pulse between two of the electrodes.

In one embodiment, lead 100 is adapted for septal placement of one or more of the electrodes while utilizing pulmonary artery 22 for lead fixation. By using the pulmonary artery, the lead can be implanted such that the electrode contacts the upper portion of septum 18 above apex 17 without requiring active fixation. Lead 100 can thus shock, pace, and sense at the interventricular septum 18 or ventricular outflow tract 20.

For example, in one embodiment electrode 122 is coupled to intermediate portion 111 of the lead. Electrode 122 can be a defibrillation electrode, such as a coil defibrillation electrode designed to deliver a defibrillation shock of approximately 10 joules to approximately 50 joules to septum 18 from the pulse generator. Electrode 122 can also deliver cardioversion shocks of approximately 0.1 joules to approximately 10 joules. In one example, electrode 122 can be a spring or coil defibrillation electrode.

When present leads are inserted in the heart and positioned such that an electrode is against the high ventricular septum (above the apex 17), the leads require active fixation. However, active fixation can cause repeated trauma to the endocardial tissue because of the cyclical motion of the heart, and thus may have possible micro-dislodgement and increase defibrillation and pacing thresholds.

In one embodiment of the present system, distal end 109 of lead 100 includes a pre-formed, biased shape 130 adapted to passively fixate distal end 109 of the lead within pulmonary artery 22 with electrode 122 positioned in the right ventricle or ventricular outflow tract. In one embodiment, pre-formed, biased shape 130 includes an S-shaped configuration 132. The pre-formed, biased shape 130 generally includes at least two lead surfaces (such as surfaces 132 and 136, for example) which are dimensioned and positionable such that the surfaces contact opposing walls of the pulmonary artery.

In various embodiments, pre-formed bias shape 130 can include a curved shape such as an S-shape, a C-shape, a J-shape, an O-shape, and other non-linear shapes adapted for contacting one or more sides of the pulmonary artery to provide sufficient fixation of the lead. Such a design is more reliable because the lead becomes easier to implant and explant because of the passive fixation which is allowed by the shape of distal portion of lead 100. Moreover, passive fixation allows for easier adjustment of the electrode placement. Also, there is less trauma or perforation to endocardium tissue, which can yield lower pacing thresholds, and there is less trauma to the high septal or outflow tract than caused by active fixation at the high septal or outflow tract location. To form pre-formed biased shape 130, the lead body can be manufactured in the pre-biased shape or the conductor coil can be formed in the pre-biased shape to thus bias the lead body.

In one embodiment, electrodes 124 and 126 of lead 100 can include pacing/sensing electrodes, such as ring electrodes located distally from electrode 122. Electrodes 124 and 126 are proximal from distal end 109 and are located on the lead to sense or pace at the ventricular septum or the ventricular outflow tract when the lead is implanted.

In one embodiment, electrode 120 includes a second coil defibrillation electrode acting as a return electrode for electrode 122 in a bipolar system. Electrode 120 can be positioned in superior vena cava 12 or right atrium 14.

In one embodiment, at least a portion of lead 100 can include an anti-thrombosis coating 140, such as Hypren or polyethleneglycol for example. Coating 140 can be placed on the lead, for example on one or more of the distal electrodes 122, 124, 126, or on other segments of the lead.

In one embodiment, lead 100 can include a sensor 150, such as a cardiac output sensor, mounted proximate a distal segment of the lead or mounted on the intermediate portion of the lead. Sensor 150 is implanted to a location within the pulmonary artery or within the outflow tract 20 to monitor cardiac output through pulmonary artery 22. For example, a cardiac output monitoring sensor 150 can be placed proximate the distal end of the lead to measure cardiac output through the pulmonary artery. Sensor 150 can be coupled to pulse generator 110 through a conductor.

In one embodiment, sensor 150 can be a flow speed sensor, allowing the system to know how fast the blood is going through the artery. For example, sensor 150 can be a metal ring or coil. Such a component would have resistance properties such that if a pulse of energy was sent through the component, the component would heat up, which would in turn increase the electrical resistance of the component. The electrical resistance could be monitored over time to determine how it changes as the blood flow going past it cools it down to blood temperature. The faster the blood flow, the faster the component will cool down and hence the faster the resistance should drop. This cool down or resistance change can be correlated to the blood flow. In other embodiments, sensor 150 can be a pressure sensor. In some embodiments, sensor 150 can include a CO₂ or O₂ sensor.

In these embodiments, sensor 150 can be used to determine blood flow to allow the position of electrodes 122, 124, and 126 to be optimized. For example, the cardiac output can be used to change the position of the electrode either during or after implantation. In some examples, sensor 150 can be used to help optimize the location of other electrodes on separate leads located within the heart. Moreover, sensor 150 can be used to provide pacing and sensing information to the pulse generator to deliver pulses or modify the settings of the pulse generator.

In some embodiments, lead 100 can be configured to allow both a stylet or catheter delivery. For example, an opening can be left through the middle of the lead to allow a stylet to be used.

FIG. 2 shows distal portion 109 of lead 100 according to one embodiment. In this example, pre-formed, biased shape 130 includes a J-shaped curve 142 at a distal tip of the lead body. J-shaped curve 142 can be positioned within pulmonary artery 22 or in one of the branch arteries off of the pulmonary artery to passively fixate the distal end of the lead within the pulmonary artery.

FIG. 3 shows distal portion 109 of lead 100 according to one embodiment. In this example, pre-formed, biased shape 130 includes a spiral configuration 144.

FIG. 4 shows distal portion 109 of lead 100 according to one embodiment. In this example, pre-formed, biased shape 130 includes a C-shaped configuration 146.

FIG. 5 shows a view of a lead 200 according to one embodiment. Lead 200 includes some of the components discussed above for lead 100, and the above discussion is incorporated herein. Lead 200 is implanted in heart 10 with distal end 109 located within pulmonary artery 22 and electrode 122 positioned against septum 18 or within ventricular outflow tract 20.

In one embodiment, lead 200 includes a lead body 210 including a pre-formed J-shape 220 formed in the intermediate portion 111 of the lead body. J-shape 220 is located such that electrode 122 is located distally from a bottom 222 of the pre-formed J-shape 220. Various embodiments includes a pre-formed J-shape in either 2D or 3D. J-shaped portion 220 of lead 200 allows for better septal/electrode contact. To pre-form the lead, the lead can be manufactured such that it is biased in the J-shape. Thus, the lead naturally reverts to the J-shape when it is implanted. For example, the lead body can be formed in the pre-biased shape or the conductor coils can be formed in the pre-biased shape to bias the lead body into the shape. When implanted, the bottom 222 of the J-shape 220 is within the right ventricle 16 and electrode 122 is positioned proximate ventricular septum 18 or right ventricular outflow tract 20 such that at least a portion of the distal end 109 of the lead body is located within a pulmonary artery 22. The pre-formed J-lead design enhances the septal electrode stability and contact, and can help result in lower defibrillation and pacing thresholds because of better electrode contacts.

In one embodiment, a second electrode 120 is located proximally from the bottom 222 of the J-shape and positioned to be located within superior vena cava 12 or right atrium 14 when the distal end 109 of the lead is within the pulmonary artery 22. Lead 200 can also include one or more pacing/sensing electrodes 124, 126 located distally from electrode 122 to sense or pace at the ventricular septum 18 or the ventricular outflow tract 20. One embodiment includes a sensor 150, such as a cardiac output sensor. In this example, sensor 150 is located within the outflow tract 150.

In one embodiment, distal end 109 is adapted for being fixated within a pulmonary artery. One embodiment provides a passive fixation technique, as described above in FIGS. 1-4. For example, a pre-formed biased distal portion 250 can be provided. In some embodiments, to be discussed below, an active fixation technique is utilized. Some embodiments utilize neither passive nor active fixation, relying on the J-shape 220 and gravity to hold the electrodes 122, 124, and 126 in place against the septum or the outflow tract.

FIG. 6 shows a front view of a lead 300 according to one embodiment. Lead 300 includes some of the components discussed above for leads 100 and 200, and the above discussion is incorporated herein. Lead 300 can be implanted in a heart (not shown) with distal end 109 located within the pulmonary artery and electrode 122 positioned against the septum or within the ventricular outflow tract.

In one embodiment, lead 300 includes a section 310 of the intermediate section 111 of the lead which is less stiff, or more pliable, than adjacent sections 312 and 316 of the lead body. Less stiff section 310 is located proximally from electrode 122 and proximally from electrode 120. When lead 300 is positioned in the heart with distal portion 109 in the pulmonary artery, the soft, or less stiff section 310 allows the lead to naturally fall into place and contact the septum due to gravity. Lead 300 is adapted to be placed within a heart in a J-shaped configuration with the less stiff section 310 near a bottom 318 of the J-shape such that electrode 122 is positioned proximate a ventricular septum or a right ventricular outflow tract and at least a portion of the distal end 109 of the lead body is located within a pulmonary artery. The less stiff section 310 helps reduce any forces caused by heart motion to be transferred to a site of the septal electrode.

In one embodiment, the less stiff section 310 includes a different, more pliable material than the material of adjacent sections 312 and 316. Again, when the lead is positioned in the heart, the softer segment allows the lead to naturally fall into place and contact the septum due to gravity, and thus enhances the septal electrode stability and contact and reduces or eliminates the forces and motion (caused by heart motion) transferred to the site of the septal electrode 122. This can result in lower defibrillation and pacing thresholds because of better electrode contact.

In this example, no fixation technique is shown in the pulmonary artery for lead 300. In other embodiments, a passive technique as shown above in FIGS. 1-5, or the active technique discussed below can be utilized.

FIG. 7 shows a portion of lead 300 according to one embodiment. In this embodiment, less stiff section 310 includes a smaller diameter than the adjacent sections 312 and 314. The smaller diameter section 310 is more flexible than the adjacent thicker regions.

In other embodiments, less stiff section 310 can be formed by providing a lead wall having a different internal diameter thickness, or by providing a less stiff conductor coil at that location.

In one example use of one or more of the leads discussed herein, the lead is inserted through the right ventricle 16 and into the pulmonary artery 22 using a guiding catheter or a stylet. The lead is positioned until the distal end of the lead is in the pulmonary artery and electrodes 122, 124, and 126 are positioned against the septum or within the outflow tract. The distal end of the lead can be fixated within the artery by one of the techniques discussed above. The pulse generator can be used to sense the activity of the heart using electrodes 124 and 126, for example. When there is need for a cardioversion or defibrillation shock, the shock is delivered via electrode 122. As discussed, in various examples, the lead body can be configured in a pre-formed J-shape such that shock electrode is located distally from a bottom of the J-shape, or a less stiff section can be provided.

FIG. 8 shows a view of a lead 400 according to one embodiment, implanted within a heart 10. Lead 400 is adapted to be actively fixated within the pulmonary artery 22 utilizing a helix 410, or other fixation mechanism. In one embodiment, lead 400 includes radiopaque markers 420 near the distal tip to help a physician guide the lead when viewed under fluoroscopy. One embodiment includes a drug elution member 430, which can elude steroids, for example, to reduce inflammatory response of the tissue. In some embodiments, lead 400 does not include either the pre-formed J-shape 220 (FIG. 5) or the less stiff section 310 (FIG. 6) of the leads discussed above. Lead 400 can be an unbiased, flexible lead relying on helix 410 for fixation within the pulmonary artery. In other embodiments, the active fixation technique can be used with the leads discussed above. In some embodiments, active fixation can be provided in addition to or in place of the passive fixation design discussed above.

It is understood that the above description is intended to be illustrative, and not restrictive. Many other embodiments will be apparent to those of skill in the art upon reviewing the above description. The scope of the invention should, therefore, be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled. 

1. A lead comprising: a lead body extending from a proximal end to a distal end and having an intermediate portion; and an electrode coupled to the intermediate portion of the lead; wherein the distal end of the lead includes a pre-formed, biased shape adapted to passively fixate the pre-formed biased shape of the distal end of the lead within a pulmonary artery with the electrode positioned in the right ventricle or ventricular outflow tract; and wherein the intermediate portion of the lead includes a lead configuration structure which configures the lead such that the electrode is moved towards a ventricular septum when the distal end of the lead is within the pulmonary artery and the electrode is positioned in the right ventricle or ventricular outflow tract.
 2. The lead of claim 1, wherein the pre-formed, biased shape includes an S-shaped configuration.
 3. The lead of claim 1, wherein the pre-formed, biased shape includes a C-shaped configuration.
 4. The lead of claim 1, wherein the pre-formed, biased shape includes a spiral configuration.
 5. The lead of claim 1, wherein the pre-formed, biased shape includes a J-shaped curve at a distal tip of the lead body.
 6. The lead of claim 1, wherein the pre-formed, biased shape includes at least two surfaces positioned to contact opposing walls of the pulmonary artery.
 7. The lead of claim 1, wherein the pre-formed, biased shape includes at least one curve in the lead body dimensioned such that at least two lead surfaces on the distal end of the lead contact at least two walls of the pulmonary artery.
 8. The lead of claim 1, wherein the lead configuration structure includes a pre-formed J-shape, wherein the electrode is located distally from a bottom of the pre-formed J-shape.
 9. The lead of claim 1, wherein the lead configuration structure includes a section of the intermediate portion of the lead body which is less stiff than adjacent sections of the lead body, the less stiff section located proximally from the electrode.
 10. The lead of claim 1, wherein electrode includes a defibrillation coil electrode.
 11. The lead of claim 1, further comprising a pacing/sensing electrode located distally from the electrode to sense or pace within the ventricular septum or the ventricular outflow tract.
 12. The lead of claim 1, wherein at least a portion of the lead includes an anti-thrombosis coating.
 13. The lead of claim 1, further comprising a sensor mounted to the distal end to monitor cardiac output through the pulmonary artery.
 14. A lead comprising: a lead body extending from a proximal end to a distal end and having an intermediate portion; an electrode coupled to the intermediate portion of the lead; means for passively fixating the distal end of the lead within a pulmonary artery, wherein the distal end of the lead includes a pre-formed shape section to passively fixate the pre-formed shape section within the pulmonary artery; and wherein the intermediate portion of the lead includes a lead configuration structure which configures the lead such that the electrode is moved towards a ventricular septum when the distal end of the lead is within the pulmonary artery and the electrode is positioned in the right ventricle or ventricular outflow tract.
 15. The lead of claim 14, wherein means for passively fixating include the distal end of the lead having an S-shaped configuration.
 16. The lead of claim 14, wherein means for passively fixating include the distal end of the lead having a C-shaped configuration.
 17. The lead of claim 14, wherein means for passively fixating include the distal end of the lead having a spiral configuration.
 18. The lead of claim 14, wherein means for passively fixating include the distal end of the lead having a J-shaped curve at a distal tip of the lead body.
 19. The lead of claim 14, wherein means for passively fixating include the distal end of the lead having at least two surfaces positioned to contact opposing walls of the pulmonary artery.
 20. The lead of claim 14, wherein means for passively fixating include the distal end of the lead having at least one curve in the lead body dimensioned such that at least two lead surfaces on the distal end of the lead contact at least two walls of the pulmonary artery.
 21. A lead comprising: a lead body extending from a proximal end to a distal end and having an intermediate portion, wherein the lead body is configured into a pre-formed J-shape; and an electrode coupled to the intermediate portion of the lead body and located distally from a bottom of the pre-formed J-shape, wherein the lead is adapted to be placed within a heart in a J-shaped configuration with the bottom of the J-shape within the right ventricle and the electrode positioned proximate a ventricular septum or a right ventricular outflow tract such that at least a portion of the distal end of the lead body is located within a pulmonary artery, wherein the distal end of the lead includes a pre-formed, biased shape adapted to fixate the distal end of the lead within the pulmonary artery when the pre-formed biased shape is within the pulmonary artery.
 22. The lead of claim 21, wherein the distal end of the lead is adapted to be passively fixated within the pulmonary artery.
 23. The lead of claim 21, wherein the distal end of the lead is adapted to be actively fixated within the pulmonary artery.
 24. The lead of claim 21, further comprising a second electrode located proximally from the bottom of the J-shape and positioned to be located within a superior vena cava or right atrium when the distal end of the lead is within the pulmonary artery.
 25. The lead of claim 21, further comprising a pacing/sensing electrode located distally from the electrode to sense or pace within the ventricular septum or the ventricular outflow tract.
 26. The lead of claim 21, wherein at least a portion of the lead includes an anti-thrombosis coating.
 27. The lead of claim 21, further comprising a sensor mounted proximate the distal end of the lead body to monitor cardiac output through the pulmonary artery.
 28. A lead comprising: a lead body extending from a proximal end to a distal end and having an intermediate section, the distal end being adapted for being fixated within a pulmonary artery; and an electrode mounted to the intermediate section of the lead body; wherein the lead body includes a pre-formed J-shape with a base of the J-shaped lead body being proximally located relative to the electrode such that the electrode contacts a ventricular septum when the lead is positioned in a heart with the intermediate section within the right ventricle and the distal end fixated within the pulmonary artery, wherein the distal end of the lead includes a pre-formed, biased shape adapted to passively fixate the distal end of the lead within the pulmonary artery when the pre-formed biased shape is within the pulmonary artery.
 29. The lead of claim 28, wherein the distal end of the lead includes an S-shaped configuration.
 30. The lead of claim 28, wherein the electrode includes a defibrillation coil electrode.
 31. The lead of claim 28, further comprising a pacing/sensing electrode located distally from the electrode to sense or pace within the ventricular septum or the ventricular outflow tract.
 32. A lead comprising: a lead body extending from a proximal end to a distal end and having an intermediate portion, wherein a section of the intermediate portion of the lead body is less stiff than adjacent sections of the lead body; and an electrode coupled to the intermediate portion of the lead body and located distally from the less stiff section, wherein the lead is adapted to be placed within a heart in a J-shaped configuration with the less stiff section near a bottom of the J-shape such that the electrode is positioned proximate a ventricular septum or a right ventricular outflow tract and at least a portion of the distal end of the lead body is located within a pulmonary artery.
 33. The lead of claim 32, wherein the less stiff section includes a different material than the adjacent sections.
 34. The lead of claim 32, wherein the less stiff section has a smaller diameter than the adjacent sections.
 35. The lead of claim 32, wherein the distal end of the lead is adapted to be passively fixated within the pulmonary artery.
 36. The lead of claim 32, wherein the distal end of the lead is adapted to be actively fixated within the pulmonary artery.
 37. The lead of claim 32, further comprising a second electrode located proximally from the less stiff section such that the second electrode is within the superior vena cava or right atrium when the distal end of the lead is within the pulmonary artery.
 38. The lead of claim 32, further comprising a pacing/sensing electrode located distally from the electrode to sense or pace within the ventricular septum or the ventricular outflow tract.
 39. The lead of claim 32, wherein at least a portion of the lead includes an anti-thrombosis coating.
 40. The lead of claim 32, further comprising a sensor mounted proximate the distal end of the lead body to monitor cardiac output through the pulmonary artery.
 41. A lead comprising: a lead body extending from a proximal end to a distal end and having an intermediate section, the distal end being adapted for being fixated within a pulmonary artery; and an electrode mounted to the intermediate section of the lead body; wherein the intermediate section of the lead body includes a less stiff section relative to adjacent sections of the lead body, the less stiff section being proximally located relative to the electrode, such that the electrode contacts a ventricular septum when the lead is positioned in a heart with the intermediate section within the right ventricle and the distal end fixated within the pulmonary artery.
 42. The lead of claim 41, wherein the distal end of the lead includes a biased pre-formed shape adapted for passively fixating the distal end within a pulmonary artery.
 43. The lead of claim 41, wherein the electrode includes a defibrillation coil electrode.
 44. The lead of claim 41, further comprising a pacing/sensing electrode located distally from the electrode to sense or pace within the ventricular septum or the ventricular outflow tract.
 45. The lead of claim 41, wherein the less stiff section includes a different material than the adjacent sections.
 46. The lead of claim 41, wherein the less stiff section has a smaller diameter than the adjacent sections. 